1. Field of the Invention
This invention relates generally to turbines and the like having shafts journalled for high speed rotation in bearings, and is concerned in particular with an improvement in the lubrication of such bearings.
2. Description of the Prior Art
In a conventional system for lubricating ball bearings, the lower portion of the bearing assembly is submerged in an underlying bath of liquid lubricant, e.g., oil. This produces satisfactory results at relatively low operating speeds. However, at higher operating speeds on the order of those encountered in turbine applications, severe problems are encountered. For example, the submerged bearing components churn and impart turbulence to the oil bath, and an increase in fluid friction within the bearing is experienced. This in turn results in excessive operating temperatures. Moreover, the turbulence in the oil bath causes oil to be thrown out through the seals, making it difficult to maintain the oil at an optimum level for efficient lubrication.
In an attempt at avoiding these problems, the system shown in FIG. 1 has been developed for certain high speed turbine applications. Here the turbine shaft 10 is rotatably journalled in a ball bearing assembly 12 enclosed in a housing 14. The housing has a base portion 16 which defines a sump 18 underlying the shaft, and a cap 20 which cooperates with a retainer portion 22 of the housing to hold the bearing assembly in place. The sump 16 is adapted to contain a supply 24 of liquid lubricant. In order to avoid excessive churning and frothing of the lubricant, the lubricant surface is maintained at a level beneath that of the rotating shaft and the rotatable bearing components. A sleeve 26 is fixed to the shaft at a location directly adjacent to the bearing, and a ring 28 is suspended from the sleeve. The ring 28 has a diameter considerably greater than that of the sleeve 26, and the lower ring portion dips downwardly into the liquid lubricant 24 in the sump.
As the shaft 10 and sleeve 26 rotate, the frictional contact between the sleeve and the ring 28 causes the latter to rotate about its axis. Lubricant is carried upwardly from the sump by the rotating sleeve, and some of the thus carried lubricant ultimately finds its way to the bearing before being returned to the sump by centrifugal and/or gravitational forces.
The difficulty with this arrangement is that the application of lubricant to the bearing is at best intermittent, somewhat haphazard, and thus relatively inefficient. Under high speed operating conditions such as those encountered in turbines and the like, reliability can be seriously compromised by the shortened bearing life resulting not only from inefficient lubrication, but more importantly from the insufficient dissipation of heat from the bearing assembly.
The objective of the present invention is to overcome the above described problems by providing a more reliable and efficient means of continuously supplying lubricant to the bearing.